Recently, several hew sea life species, including a prolific European mussel known as the zebra mussel, have been discovered in North American waters. These recent immigrees have probably entered the North American waters as a result of discharges of freshwater ballast from ocean-crossing ships. While many new species will disturb the ecological relationships among native biota, the zebra mussel will probably be the species imparting the greatest devastation to the waters.
The zebra mussel or Dreissena polymorpha is a bivalve mollusk native to Europe. This organism has been unintentionally introduced into North American waters by the discharge of ballast water from transoceanic ships. The mollusk is generally discharged from the ballast in the form of larvae, but quickly grows to adult size. As adults, the zebra mussels continue to spread rapidly because the adults produce a free-floating reproductive stage called a veliger. Veligers are planktonic young that are produced for approximately six to eight months per year in temperate latitudes and are capable of drifting in currents for up to thirty days. Moreover, the mobility of the veliger in combination with the high fecundity of the female mussels can result in more than 60,000 veligers/m.sup.2 which are capable of colonizing any firm substrate. With currents as the major dispersal mechanism to downstream areas, and the ability of veligers to attach themselves to boats as a dispersal mechanism to upstream areas, their rate of spread is fast and extensive.
The zebra mussel is not only harmful to water systems because of its extreme mobility and fecundity but also because it is equipped with a byssal apparatus that secretes horny threads and enables the mussel to climb and firmly attach itself to any solid surface. As a consequence, these mussels have already attached themselves to the submerged parts of municipal water systems, including intake pipes, which has greatly restricted the inflow of water to electrical generating and water treatment facilities by reducing the diameter of the intake pipes. When the diameter of the intake pipes is reduced, the influx of water volume through these same pipes drastically decreases. This reduced water flow through the pipes is partially due to the fact that zebra mussel larvae are approximately 200 micromesh which allows for the larvae to easily pass through the intake pipe screens and infest the interior of the intake pipes. The reduced water flow through the intake pipes is further complicated by the fact that these mussels have also attached themselves to the screens that cover the intake pipes, which further contributes to the blockage problem.
As these mussels are capable of colonizing any firm substrate, the mussels found on the intake pipes and intake pipe screens form colonies that are several inches thick. The intake pipes and intake pipe screens are exceptionally good for mussel colonization due to the abundance of food near intake pipes resulting from the presence of the intake pipe screens which function, in part, to filter out food from the flowing water. Thus, as these mussels continue to be dispersed throughout the waters, the intake pipes and screens of water systems, which are essential to water usage, will continue to be obstructed unless these mussels are eliminated immediately.
Some effort has been made, to date, to combat the zebra mussel problem. These efforts have included the installation of chlorination units at the water pump station. This proved ineffective, as the release of the chlorine at the pump house was unsafe without the installation of chlorine detection controls. Other efforts that have been considered for combating the zebra mussel problem include building an overland pipeline from the lake to the water system so as to provide an additional water source. This solution, however, is not economically feasible.
Accordingly, an object of the present invention is to provide a preventative maintenance system for protecting underwater pipes from zebra mussel and other sea life infestation that eliminates the mussels in both their adult and larvae stage.
Another object of the invention is to provide a preventative maintenance system for protecting underwater pipes from zebra mussel infestation that is compatible with existing intake pipes and screens.
Another object of the invention is to provide a preventative maintenance system for protecting underwater pipes from zebra mussel infestation that is assembled directly onto the intake pipes and screens.
Another object of the invention is to provide a preventative maintenance system for protecting underwater pipes from zebra mussel infestation having an underwater flexible feed piping that extends the length of the intake pipe and which is assembled in that portion of the intake pipe without the assistance of underwater divers.
Another object of the invention is to provide a preventative maintenance system for protecting underwater pipes from zebra mussel infestation having an apparatus that is mounted on the intake pipe or intake pipe screen and which is capable of withstanding the heavy volume of water flowing past same.
A further object of the invention is to provide a preventative maintenance system for protecting underwater pipes from mussel infestation that is relatively easy to construct and fast to assemble onto extant intake pipes and screens.